var datePickerDivID = "datepicker";
var iFrameDivID = "datepickeriframe";
var dayArrayShort = new Array('Su', 'Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa');
var dayArrayMed = new Array('Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat');
var dayArrayLong = new Array('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday');
var monthArrayShort = new Array('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
var monthArrayMed = new Array('Jan', 'Feb', 'Mar', 'Apr', 'May', 'June', 'July', 'Aug', 'Sept', 'Oct', 'Nov', 'Dec');
var monthArrayLong = new Array('January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December');
var defaultDateSeparator = "-"; // common values would be "/" or "."
var defaultDateFormat = "ymd" // valid values are "mdy", "dmy", and "ymd"
var dateSeparator = defaultDateSeparator;
var dateFormat = defaultDateFormat;

function displayDatePicker(dateFieldName, displayBelowThisObject, dtFormat, dtSep)
{
    var targetDateField = document.getElementsByName (dateFieldName).item(0);

    if (!displayBelowThisObject)
        displayBelowThisObject = targetDateField;

    if (dtSep)
        dateSeparator = dtSep;
    else
        dateSeparator = defaultDateSeparator;
    // if a date format was given, update the dateFormat variable
    if (dtFormat)
        dateFormat = dtFormat;
    else
        dateFormat = defaultDateFormat;
    var x = displayBelowThisObject.offsetLeft;
    var y = displayBelowThisObject.offsetTop + displayBelowThisObject.offsetHeight ;
    // deal with elements inside tables and such
    var parent = displayBelowThisObject;
    while (parent.offsetParent) {
        parent = parent.offsetParent;
        x += parent.offsetLeft;
        y += parent.offsetTop ;
    }
    drawDatePicker(targetDateField, x, y);
}

function drawDatePicker(targetDateField, x, y)
{
    var dt = getFieldDate(targetDateField.value );

    if (!document.getElementById(datePickerDivID)) {

        var newNode = document.createElement("div");
        newNode.setAttribute("id", datePickerDivID);
        newNode.setAttribute("class", "dpDiv");
        newNode.setAttribute("style", "visibility: hidden;");
        document.body.appendChild(newNode);
    }
    // move the datepicker div to the proper x,y coordinate and toggle the visiblity
    var pickerDiv = document.getElementById(datePickerDivID);
    pickerDiv.style.position = "absolute";
    pickerDiv.style.left = x + "px";
    pickerDiv.style.top = y + "px";
    pickerDiv.style.visibility = (pickerDiv.style.visibility == "visible" ? "hidden" : "visible");
    pickerDiv.style.display = (pickerDiv.style.display == "block" ? "none" : "block");
    pickerDiv.style.zIndex = 10000;
    // draw the datepicker table
    refreshDatePicker(targetDateField.name, dt.getFullYear(), dt.getMonth(), dt.getDate());
}
/**
This is the function that actually draws the datepicker calendar.
*/
function refreshDatePicker(dateFieldName, year, month, day)
{
    // if no arguments are passed, use today's date; otherwise, month and year
    // are required (if a day is passed, it will be highlighted later)
    var thisDay = new Date();
    if ((month >= 0) && (year > 0)) {
        thisDay = new Date(year, month, 1);
    } else {
        day = thisDay.getDate();
        thisDay.setDate(1);
    }

    var crlf = "\r\n";
    var TABLE = "<table cols=7 class='dpTable'>" + crlf;
    var xTABLE = "</table>" + crlf;
    var TR = "<tr class='dpTR'>";
    var TR_title = "<tr class='dpTitleTR'>";
    var TR_days = "<tr class='dpDayTR'>";
    var TR_todaybutton = "<tr class='dpTodayButtonTR'>";
    var xTR = "</tr>" + crlf;
    var TD = "<td class='dpTD' onMouseOut='this.className=\"dpTD\";' onMouseOver=' this.className=\"dpTDHover\";' "; // leave this tag open, because we'll be adding an onClick event
    var TD_title = "<td colspan=5 class='dpTitleTD'>";
    var TD_buttons = "<td class='dpButtonTD'>";
    var TD_todaybutton = "<td colspan=7 class='dpTodayButtonTD'>";
    var TD_days = "<td class='dpDayTD'>";
    var TD_selected = "<td class='dpDayHighlightTD' onMouseOut='this.className=\"dpDayHighlightTD\";' onMouseOver='this.className=\"dpTDHover\";' "; // leave this tag open, because we'll be adding an onClick event
    var xTD = "</td>" + crlf;
    var DIV_title = "<div class='dpTitleText'>";
    var DIV_selected = "<div class='dpDayHighlight'>";
    var xDIV = "</div>";
    // start generating the code for the calendar table
    var html = TABLE;
    // this is the title bar, which displays the month and the buttons to
    // go back to a previous month or forward to the next month
    html += TR_title;
    html += TD_buttons + getButtonCode(dateFieldName, thisDay, -1, "&lt;") + xTD;
    html += TD_title + DIV_title + monthArrayLong[ thisDay.getMonth()] + " " + thisDay.getFullYear() + xDIV + xTD;
    html += TD_buttons + getButtonCode(dateFieldName, thisDay, 1, "&gt;") + xTD;
    html += xTR;
    // this is the row that indicates which day of the week we're on
    html += TR_days;
    for(i = 0; i < dayArrayShort.length; i++)
        html += TD_days + dayArrayShort[i] + xTD;
    html += xTR;
    // now we'll start populating the table with days of the month
    html += TR;
    // first, the leading blanks
    for (i = 0; i < thisDay.getDay(); i++)
        html += TD + "&nbsp;" + xTD;
    // now, the days of the month
    do {
        dayNum = thisDay.getDate();
        TD_onclick = " onclick=\"updateDateField('" + dateFieldName + "', '" + getDateString(thisDay) + "');\">";
        if (dayNum == day)
            html += TD_selected + TD_onclick + DIV_selected + dayNum + xDIV + xTD;
        else
            html += TD + TD_onclick + dayNum + xTD;
        // if this is a Saturday, start a new row
        if (thisDay.getDay() == 6)
            html += xTR + TR;
        // increment the day
        thisDay.setDate(thisDay.getDate() + 1);
    } while (thisDay.getDate() > 1)
    // fill in any trailing blanks
    if (thisDay.getDay() > 0) {
        for (i = 6; i > thisDay.getDay(); i--)
            html += TD + "&nbsp;" + xTD;
    }
    html += xTR;
    // add a button to allow the user to easily return to today, or close the calendar
    var today = new Date();
    var todayString = "Today is " + dayArrayMed[today.getDay()] + ", " + monthArrayMed[ today.getMonth()] + " " + today.getDate();
    html += TR_todaybutton + TD_todaybutton;
    html += "<button class='dpTodayButton' onClick='refreshDatePicker(\"" + dateFieldName + "\");'>this month</button> ";
    html += "<button class='dpTodayButton' onClick='updateDateField(\"" + dateFieldName + "\");'>close</button>";
    html += xTD + xTR;
    // and finally, close the table
    html += xTABLE;
    document.getElementById(datePickerDivID).innerHTML = html;
    // add an "iFrame shim" to allow the datepicker to display above selection lists
    adjustiFrame();
}
/**
Convenience function for writing the code for the buttons that bring us back or forward
a month.
*/
function getButtonCode(dateFieldName, dateVal, adjust, label)
{
    var newMonth = (dateVal.getMonth () + adjust) % 12;
    var newYear = dateVal.getFullYear() + parseInt((dateVal.getMonth() + adjust) / 12);
    if (newMonth < 0) {
        newMonth += 12;
        newYear += -1;
    }
    return "<button class='dpButton' onClick='refreshDatePicker(\"" + dateFieldName + "\", " + newYear + ", " + newMonth + ");'>" + label + "</button>";
}

function getDateString(dateVal)
{
    var dayString = "00" + dateVal.getDate();
    var monthString = "00" + (dateVal.getMonth()+1);
    dayString = dayString.substring(dayString.length - 2);
    monthString = monthString.substring(monthString.length - 2);
    switch (dateFormat) {
        case "dmy" :
            return dayString + dateSeparator + monthString + dateSeparator + dateVal.getFullYear();
        case "ymd" :
            return dateVal.getFullYear() + dateSeparator + monthString + dateSeparator + dayString;
        case "mdy" :
        default :
            return monthString + dateSeparator + dayString + dateSeparator + dateVal.getFullYear();
    }
}
/**
Convert a string to a JavaScript Date object.
*/
function getFieldDate(dateString)
{
    var dateVal;
    var dArray;
    var d, m, y;
    try {
        dArray = splitDateString(dateString);
        if (dArray) {
            switch (dateFormat) {
                case "dmy" :
                    d = parseInt(dArray[0], 10);
                    m = parseInt(dArray[1], 10) - 1;
                    y = parseInt(dArray[2], 10);
                    break;
                case "ymd" :
                    d = parseInt(dArray[2], 10);
                    m = parseInt(dArray[1], 10) - 1;
                    y = parseInt(dArray[0], 10);
                    break;
                case "mdy" :
                default :
                    d = parseInt(dArray[1], 10);
                    m = parseInt(dArray[0], 10) - 1;
                    y = parseInt(dArray[2], 10);
                    break;
            }
            dateVal = new Date(y, m, d);
        } else if (dateString) {
            dateVal = new Date(dateString);
        } else {
            dateVal = new Date();
        }
    } catch(e) {
        dateVal = new Date();
    }
    return dateVal;
}

function splitDateString(dateString)
{
    var dArray;
    if (dateString.indexOf("/") >= 0)
        dArray = dateString.split("/");
    else if (dateString.indexOf(".") >= 0)
        dArray = dateString.split(".");
    else if (dateString.indexOf("-") >= 0)
        dArray = dateString.split("-");
    else if (dateString.indexOf("\\") >= 0)
        dArray = dateString.split("\\");
    else
        dArray = false;
    return dArray;
}

function updateDateField(dateFieldName, dateString)
{
    var targetDateField = document.getElementsByName (dateFieldName).item(0);
    if (dateString)
        targetDateField.value = dateString;
    var pickerDiv = document.getElementById(datePickerDivID);
    pickerDiv.style.visibility = "hidden";
    pickerDiv.style.display = "none";
    adjustiFrame();
    targetDateField.focus();
    // after the datepicker has closed, optionally run a user-defined function called
    // datePickerClosed, passing the field that was just updated as a parameter
    // (note that this will only run if the user actually selected a date from the datepicker)
    if ((dateString) && (typeof(datePickerClosed) == "function"))
        datePickerClosed(targetDateField);
}

function adjustiFrame(pickerDiv, iFrameDiv)
{
    // we know that Opera doesn't like something about this, so if we
    // think we're using Opera, don't even try
    var is_opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
    if (is_opera)
        return;
    // put a try/catch block around the whole thing, just in case
    try {
        if (!document.getElementById(iFrameDivID)) {
            var newNode = document.createElement("iFrame");
            newNode.setAttribute("id", iFrameDivID);
            newNode.setAttribute("src", "javascript:false;");
            newNode.setAttribute("scrolling", "no");
            newNode.setAttribute ("frameborder", "0");
            document.body.appendChild(newNode);
        }
        if (!pickerDiv)
            pickerDiv = document.getElementById(datePickerDivID);
        if (!iFrameDiv)
            iFrameDiv = document.getElementById(iFrameDivID);
        try {
            iFrameDiv.style.position = "absolute";
            iFrameDiv.style.width = pickerDiv.offsetWidth;
            iFrameDiv.style.height = pickerDiv.offsetHeight ;
            iFrameDiv.style.top = pickerDiv.style.top;
            iFrameDiv.style.left = pickerDiv.style.left;
            iFrameDiv.style.zIndex = pickerDiv.style.zIndex - 1;
            iFrameDiv.style.visibility = pickerDiv.style.visibility ;
            iFrameDiv.style.display = pickerDiv.style.display;
        } catch(e) {
        }
    } catch (ee) {
    }
}
